1. Field of the Invention
The present invention relates to a key operated rotary switch particularly adapted for enabling and disabling an automobile air bag supplemental restraint system.
2. Discussion of the Background
Airbag supplemental restraint systems have been widely used to protect automobile occupants in the event of a front impact collision. Typically an airbag unit will be located in an automobile's steering wheel and another will be located in the dashboard opposite the front passenger seat. During a crash, impact sensors located in the car's bumper will sense the onset of the collision and send an electrical signal to the airbags. The electrical signals ignite small explosive charges within each airbag unit, and the ensuing controlled explosions generate large amounts of expanding gases which rapidly inflate the airbags, thereby forming a gaseous cushion to protect the driver and/or a passenger riding in the front of the car.
While airbags have been very successful in preventing injuries and death, it has also been found that under certain conditions the airbags themselves may pose a potential safety hazard due to the explosive force with which they are deployed. Generally these situations are limited to those where the driver and/or the front seat passenger are relatively small in physical stature, or when small children are placed in the front seat of the vehicle. In these cases, the explosive force of the airbag deployment is sufficient to cause severe impact injuries to the passenger which the airbag unit is putatively designed to protect. Thus, in these situations it may be desirable to selectively disable one or more of the front airbags.
In the majority of cases, the safest mode of operating the vehicle will be to have all of the automobile's airbag systems enabled. However, in those rare occasions when the operator of the vehicle has determined that it is safer to disarm one or more of the airbag units, an interface must be provided whereby the operator may interact with the airbag system to selectively enable or disable the various airbag units. A manually operated switch may provide such an interface, however, the addition of such a switch raises a number of safety concerns which must be considered before such a switch may be safely integrated into the airbag system.
A first issue raised by adding a disabling switch to the airbag system is how to limit access to the switch itself. The switch must be protected such that only a limited number of responsible individuals may change the configuration of the airbag system. This is desirable so that only those individuals responsible for the vehicle, such as the owner, or the primary driver of the vehicle, may configure the airbags in a manner which they deem appropriate and feel confident that the airbags will or will not deploy as selected in the event of a collision. A simple method of controlling access to the disarm switch is to make the switch key operated, then limiting access to the key. However, adding a key switch to the passenger compartment of an automobile raises further safety issues which must also be addressed in designing a safe and effective airbag disarm switch.
A significant drawback to locating key operated switches within the passenger compartment of an automobile is that the key, when left within the switch mechanism, represents a potential source of injury to occupants of the car in the event of a collision. The sharp narrow contours of a key extending from the switch housing can cause severe puncture wounds to a human body impacting the key due to the force of the collision. In fact, the auto industry has strict homologation standards for the design of objects which protrude into the passenger compartment of a vehicle. Such objects must maintain certain minimal radial dimensions to meet the standard. Generally, a key protruding from a dash mounted airbag disarm switch is unlikely to meet this standard. Therefore, if a key switch is to be employed for enabling and disabling one or more airbags, it is desirable that the key switch include a mechanism for ejecting the key when the settings of the switch are not being manipulated.
A second problem with employing a key switch to arm and disarm an airbag, is that most standard rotary type switches can be manipulated into an ambiguous middle position between valid switch states. If this were to occur in an airbag disable switch, the operator of the vehicle could not be certain how the airbag system would deploy in the event of a collision. It is possible that airbags could deploy when they were not supposed to, or fail to deploy when it was desired that they should. In either case, the result could mean catastrophic injury to the occupants of the vehicle.
In light of these problems with the prior art, what is desired is a key operated switch which will act to expel the operating key whenever the operator physically releases the key. Another feature which should be included is a positioning mechanism which will ensure that the electrical switch contacts on the switch are forced into an unambiguous switch state at all times. Such a switch would require a certain amount of external force to insert a key, for example the ignition key for starting the automobile's engine, into the airbag disarm switch and hold it there. When such force is removed, the switch should expel the key regardless of the position of the rotary mechanism within the switch. Thus, the key may tot be inadvertently left in the switch mechanism where it may pose a risk of injury to the occupants of the vehicle. With the key inserted into the switch, the key can be used to rotate the internal switch mechanism. As the rotary mechanism is rotated, the positive positioning mechanism must ensure that the switch contacts remain in a valid switch state at all times, with the transition from one state to another happening in a positive, near instantaneous manner, such that there can be no ambiguity as to which state the switch is in. The positive positioning mechanism should then ensure that the switch remains in that state until sufficient torque is applied through the key to rotate the switch into the next adjacent state. It is also desired that such a switch may be employed as a two position switch for enabling and disabling a single airbag unit, or as a four position switch for selectively enabling and disabling two airbag units.